The present invention relates to split axle drive mechanisms, and more particularly to a split axle drive mechanism for part-time four-wheel drive vehicles which include a transfer device adapted to change the operating mode of the vehicle drive system between a two wheel drive mode and a four wheel drive mode.
To reduce wear and power consumption caused by back drive of the non-driven road wheels in the two wheel drive mode, a split axle drive mechanism has been proposed in the U.S. Pat. No. 4,341,281 granted to Laszlo Nagy on July 27, 1982. The split axle drive mechainsm comprises an automotive type differential which has an input to the differential case and a pair of outputs connected to respective side gears of the differential and adapted to be connected to the respective split axle parts. One of the outputs is directly connected to one side gear of the differential, while the other output is connected to the other side gear of the differential through a clutch which is disengageable for preventing back drive to the other side gear when the vehicle is in the two wheel drive mode. In such an arrangement of the split axle drive mechanism, however, the pinion gears and side gears in the differential are inevitably rotated by back drive applied thereto from one of the non-driven road wheels when the two wheel drive mode is selected at the transfer device. This results in wear of component parts in the differential.
In the U.S. Pat. No. 4,271,722 granted to Chris A. Campbell on June 9, 1981, there has been proposed a differential for a four-wheel drive vehicle which comprises an integral remotely operable axle disconnect means adapted to prevent back drive to the differential side gears when the vehicle is in the two wheel drive mode. The axle disconnect means comprises a pair of shiftable clutch collars slidably splined to each axle shaft and each having face coupling teeth engageable with opposed mating teeth on the hub of each differential side gear. The respective clutch collars are arranged to be mutually inwardly moved for engagement with the respective side gears and to be mutually outwardly moved for disengagement from the side gears. For effecting such reciprocal motion of the clutch collars, the differential further comprises an elongated control rod arranged in parallel with the differential case and axially slidably mounted within the differential housing to be driven by a single two-position actuator, a direct control arm rigidly secured at its one end to the control rod and extending toward one of the clutch collars for engagement therewith, and a lever arm linkage pivotally secured within the differential housing and having one end connected to the control rod and the other end in engagement with the other clutch collar. In such an arrangement of the two clutch collars, however, the differential housing becomes large in size due to provision of the elongated control rod for connection to the lever arm linkage.